Personal cleansing products such as soaps and detergents are used by people worldwide, resulting in an aggregate daily release of vast quantities of these materials in wastewater streams into the environment. Among products used for personal cleansing, classical soaps, i.e. the salts of fatty acids, are no longer the preferred compositions for a variety of reasons. For example, soaps are perceived to be relatively harsh or irritating to skin and eyes, are not easy to formulate in consumer-preferred formulations such as gels, do not foam well or leave skin feeling clean after use particularly when the water used in personal cleansing contains impurities such as ions, and are not particularly good vehicles for delivery of benefit agents such as fragrances. Soaps are prone to perform particularly badly in hard water, forming insoluble precipitates with ions such as Ca, Mg, Mn, and Fe that greatly interfere with cleansing.
Many compositions have been developed based on chemical substances other than classical soaps, and most include surfactants of various types, also known as syndets, that serve to solubilize oils, greases, and other soiling substances, allowing them to be washed off skin in a shower or bath. Personal cleansing compositions that are composed of surfactants other than salts of fatty acids, that provide for good foam generation, improve the perception by the user of benefit agents such as fragrances, are mild to skin, and provide a positive perception of cleansing performance, are widely used.
However, many if not all such commercial personal cleansing products contain surfactants such as anionic surfactants that can be relatively harmful to aquatic organisms especially at high concentrations and are a significant component of wastewater streams effluxed by residential units worldwide. Some of these surfactants have poor biodegradability and are thus persistent in the environment. Fragrance compounds (usually chemical mixtures, also termed fragrance oils) are another example of a component of many personal cleansing products that can be of low biodegradability and can exert a toxic effect on aquatic organisms exposed to wastewater containing residues of the fragrance compounds. The presence of these components in personal cleansing products available on the commercial market results in discharge of treated or untreated wastewater effluent containing at least some of the components into streams, rivers, oceans, and groundwater, sometimes with detrimental results.
The presence of surfactants such as anionic surfactants, and fragrance oils, in the discharged treated wastewater can be harmful to aquatic organisms in the receiving waters. The effect is more pronounced at higher concentrations of the contaminants in the wastewater. The types of organisms that can be damaged include beneficial microorganisms, invertebrate and vertebrate animals, beneficial algae, and higher plants. Also, when fresh water into which such wastewater streams are taken up for use as drinking water, the presence of such contaminants can complicate the efforts required to produce potable water for human use. See, for example the document entitled “Environmental and Health Assessment of Substances in Household Detergents and Cosmetic Detergent Products,” Torben Madsen et al., Danish Environmental Protection Agency, Centre for Integrated Environment and Toxicology (CETOX), Environmental Project No. 615, 2001, at http://www2.mst.dk/udgiv/Publications/2001/87-7944-596-9/pdV87-7944-597-7.pdf.
Aquatic toxicity and challenges to water purity are of increasing concern due to the worldwide population growth of the human population and increased per capita consumption by many individuals. Many indicator species, such as amphibians like frogs and salamanders, have exhibited alarming decreases in their populations over the last several decades. The sensitive skins of such animals may be particularly sensitive to the impact of surfactants present in their watery habitats that arise from human use. Surfactants are also know to cause problems for waterfowl, stripping the natural feather oils from the birds and rendering them prone to hypothermia. When feathers become wet due to stripping of the natural protective skin oils by surfactants, such birds are also impaired in their ability to fly. Due to the impact of surfactants on cell membranes, various aquatic invertebrates are also at risk from surfactant contamination. Oyster populations have been impacted through the discharge of surface-active synthetic compounds into marine littoral environments from sewage treatment facilities. Populations of less visible species, such as insect larvae and single-celled animals, are likely also damaged by the presence of surfactants.
Nevertheless, surfactants are extremely valuable to the human population for various washing and cleansing purposes. Frequent personal bathing and washing of hands, etc., is vital to maintaining public health, reducing the spread of pathological organisms and preventing epidemics. In general, humans appreciate being clean and appreciate cleanliness in others. Consequently, use of compositions containing surfactants is likely to continue. Therefore, it is desirable to devise cleansing compositions for personal use in bathing that are acceptable to consumers, yet reduce their impact on the environment when discharged in wastewater effluents such as bath water. By mitigating human impact on the ecosystems in which humans live, environmental sustainability of human populations can be improved without loss of any valuable and appreciated quality of life.